SPORULATION 13 



The process of direct or binary division is very simple, and 

 may be a matter of twenty minutes, or as long as six hours. 

 Division is almost always across the cell in the direction of the 

 short axis, though it may in some bacteria be in a direction 

 parallel to the long axis, but this is uncommon. 



By means of the hanging-drop or the block-culture method, 

 on an inverted cover-glass the process may be observed easily. 

 The phenomena of division begin by an elongation of the cell, 

 soon followed by a constriction of pinching in of the cell on both 

 sides, at an equatorial point. The process begins to be apparent 

 in the cell wall and extends inward. 



Division may occur in one, two, or three directions, or planes. 



By cell division bacteria multiply by geometrical progression. 

 One cell at the end of a period becomes two, and at the end of a 

 second period these two become four; at the end of another 

 period these four become eight; after twenty-four hours they 

 may number many millions. 



It is well that the food supply soon gives out and that the 

 products of bacterial metabolism, such as acids and ferments, 

 inhibit their growth. By this rapid bacterial multiplication, 

 carcasses of animals are disintegrated and the higher nitrogenous 

 compounds are reduced to simple gases that are quickly dissi- 

 pated in the air. 



SPORULATION. Sporulation is of two kinds: the first and 

 most important for hygiene is that into which some pathogenic 

 bacteria go when they meet unfavorable conditions and it affords 

 protection against all but the most vigorous disinfection; the 

 second kind is a specialized function of the higher bacteria and 

 moulds by which reproduction occurs (vegetative). In the 

 latter case it is not impossible that some sexual specialization 

 occurs. The first mentioned are called Endospores. 



Vegetative sporulation corresponds to the flowering of the 

 higher plants, and is observed under the most favorable vital 

 conditions. Endospores are produced under stress of circum- 



